Interstitial pulmonary fibrosis

Idiopathic Pulmonary Fibrosis, Cirrhosis of Lung, Postinflammatory Pulmonary Fibrosis

What is Interstitial pulmonary fibrosis?

Interstitial pulmonary fibrosis (IPF) is characterized by the replacement of normal lung tissue with fibrous tissue (fibrosis). It is just one of over 150 different interstitial lung diseases, IPF is a stiffness or scarring of the tissue in between the air sacs (alveoli) and blood vessels of the lungs. This stiffness reduces the ability of the alveoli to expand and take in adequate amounts of oxygen, leading to shortness of breath and eventually respiratory failure. Interstitial pulmonary fibrosis is irreversible and progressive. Individuals with IPF are rarely cured and become increasingly disabled. Their life expectancy after diagnosis is approximately five to ten years.

The disease may be idiopathic, or it can be triggered by a severe viral infection. An inflammation in the air sacs of the lung leads to fluid leakage and cellular breakdown. Because the healing and cleanup processes of the lung are altered, there is destruction of the walls of the air sacs and the walls of small blood vessels (capillaries), resulting in widespread scarring. The chronic nature of the disease is caused by poorly regulated macrophages (the clean up cells of the lung).

The incidence of interstitial pulmonary fibrosis is approximately five cases per 100,000. It is typically diagnosed in individuals between the ages of 40 and 60, with no preference for race, gender, or geography.

How is it diagnosed?

History: Shortness of breath is the hallmark symptom of IPF. It begins with breathlessness during exertion, which the individual may attribute to just being "out of shape. " As the disease progresses, there is shortness of breath even at rest. Other symptoms may include fatigue, dry cough, non-specific muscle and joint pain, loss of appetite, and/or weight loss.

Most important to the diagnostic process is a detailed occupational history (even as far back as a summer job in high school) to try to determine the causative exposure. History should also include hobbies or recent viral illnesses.

Physical exam: On physical exam, the individual may appear in varying degrees of respiratory distress depending on the severity or stage of the disease. Symptoms may include rapid respirations and a bluish tint to the skin, if blood oxygen levels are very low. Auscultation of the lungs (listening to breath sounds through a stethoscope) may be normal or may reveal abnormal crackling sounds. The individual may have stunted growth of the fingertips called "clubbing. " In the late stages of the disease, there may also be abnormal heart sounds associated with right-sided heart failure (cor pulmonale).

Tests: Chest x-ray is one of the first non-invasive tests ordered to begin to confirm the diagnosis of IPF. A classic pattern called "ground glass" may be detected. High-resolution computerized tomography (HRCT) can further reveal the presence and type of interstitial disease. HRCT can improve the accuracy of diagnosis from 33% to 46%. Because the medical management for Interstitial pulmonary fibrosis is prolonged and has many side effects, it is necessary to obtain an accurate diagnosis. The best accuracy is obtained with an actual sample of interstitial cells for cytological examination. To access these cells, a bronchial alveolar lavage (BAL) and/or a transbronchial biopsy is performed during a bronchoscopy (examination of the bronchi by means of a fiberoptic viewing instrument passed down the trachea). The highest level of accuracy of diagnosis, almost 95%, is obtained with tissue samples from an open lung biopsy done through an incision in the chest wall (thoracotomy).

Blood tests are usually performed to look at the immune response of the blood cells to the disease process. Blood oxygen levels, measured initially by pulse oximetry and later by arterial blood gases, are generally low. Pulmonary function tests are performed to assess the degree of impairment in the lung's mechanical ability to move air (lung volumes and flows). In IPF, lung volumes are reduced and flows may be increased. The time it takes oxygen to move from the alveoli to the capillaries across the diseased interstitial space (diffusing capacity) will be increased.

How is IPF treated?

Anti-inflammatory drugs (corticosteroids) are the mainstay of treatment for interstitial pulmonary fibrosis. A favorable response occurs in less than 25% of individuals, however, and it is desirable to wean the individual to low dose steroids after six months to a year. In individuals who are not responsive to corticosteroids, medication to suppress the action of the body's immune system (immunosuppression therapy) may be considered. Along with drug therapy, it is imperative that the individual quit smoking and be removed from any environment that might contain respiratory irritants. Due to impaired lung function, vaccinations against pneumococcal pneumonia and influenza are also important. Some individuals may develop bronchoconstriction due to scarring around the airways. Drugs may be given to help widen airway passages (bronchodilators). Individuals often benefit greatly from supplemental oxygen therapy, especially during the day when they are active. In the late stages of the disease, the individual may require medication for the treatment of right heart failure.

In individuals who have end-stage IPF that is unresponsive to medical treatment, lung transplantation may be considered.

Medications

Information Brand Generic Label Rating
Prednisone Deltasone Prednisone
Imuran Azathioprine
Cytoxan Cyclophosphamide

What might complicate it?

The following complications have been known to occur with Interstitial pulmonary fibrosis and can significantly affect disability, as well as decrease life expectancy: pneumothorax, pneumonia, heart failure, bronchitis, wound infection following open lung biopsy, side effects of corticosteroids and/or other immunosuppressive therapy, lung cancer and respiratory failure.

Predicted outcome

The outcome of pulmonary fibrosis is usually total disability followed by death within five to ten years of accurate diagnosis. In good candidates, lung transplantation during end-stage IPF has yielded a 60% two-year survival rate. The level of functioning that can be maintained with vigorous medical therapy is very individualized.

Alternatives

Once a tissue specimen is obtained for diagnosis, there is little doubt of the diagnosis. Up until that time, conditions with similar symptoms include similar interstitial lung diseases classified by the injurious agents that caused them (such as silicosis, pneumoconiosis, asbestosis), sarcoidosis (widespread granulomatous lesions in the lungs), allergic inflammation of the lungs (hypersensitivity pneumonitis), lung cancer, and bronchial obstruction.

Appropriate specialists

Pulmonologist, occupational medicine, thoracic surgeon, and immunologist.

Last updated 6 October 2011


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